1. Field of the Invention
The present invention relates to a light beam scanning apparatus, a laser machining apparatus including it, a test method for testing a light beam scanning apparatus, and a laser machining method.
2. Description of the Related Art
Light beam scanning apparatuses (galvano apparatuses) are used in machine tools such as laser drilling apparatuses, laser trimmer apparatuses, and laser repair apparatuses. A galvano apparatus has a mirror mounted on the rotation axis of a motor and causes the mirror to reflect laser light toward a target position while controlling the rotation angle of the mirror. In order to accurately set the irradiation position of laser light to a target position, it is necessary to accurately control the rotation angle of the mirror. It is possible to use an electrostatic capacitance sensor or an optical or magnetic encoder to detect the rotation angle of the mirror.
Since a machine tool is also required to operate at high speed, it is necessary to rotate/drive the mirror of a galvano apparatus at high speed. If, however, the dynamic balance between the mirror and the rotation axis of the motor is poor or the force generated by the magnet and coil of the motor contains components other than those in the rotating direction, vibration is excited in the motor in a tilt direction relative to the rotation axis of the motor. It is conventionally known that dynamic balance adjustment is performed for the rotation axis to suppress vibration in the motor (Japanese Patent Laid-Open No. 61-116632).
A detector which detects the rotation angle of the mirror of a conventional light beam scanning apparatus cannot detect vibration in a tilt direction. As a consequence, a product is machined in the presence of the vibration, and hence a machining failure can occur.